A coaxial connector plug described in Japanese Unexamined Patent Application Publication No. 2013-118121 is a known example of a coaxial connector plug of the related art. FIG. 16 is an outer perspective view of a coaxial connector plug 510 described in Japanese Unexamined Patent Application Publication No. 2013-118121.
As illustrated in FIG. 16, the coaxial connector plug 510 includes an outer conductive unit 512, a central conductor 514a, and an insulator 516. The outer conductive unit 512 includes an outer conductor 512a and outer terminals 512c and 512d. Note that the outer terminal 512c is not illustrated in FIG. 16 because the outer terminal 512c is covered by the outer conductor 512a. 
The outer conductor 512a has a shape that is substantially cylindrical and that extends in the top-bottom direction. The outer terminals 512c and 512d are drawn out beneath the outer conductor 512a, bent in a direction away from the outer conductor 512a, and disposed so as to face each other with the outer conductor 512a interposed therebetween as seen from above in plan view.
The insulator 516 has a substantially plate-like shape that has a pair of sides that oppose each other. A lower end of the outer conductor 512a is in contact with a top surface of the insulator 516, and a pair of sides of each of a pair of the outer terminals 512c and 512d are in contact with a bottom surface of the insulator 516, so that the insulator 516 is sandwiched by the outer conductive unit 512 in the top-bottom direction. The central conductor 514a is mounted on the insulator 516 and disposed in an area surrounded by the outer conductor 512a. 
A coaxial connector receptacle is to be mounted on the coaxial connector plug 510, which has the above-described configuration. More specifically, the coaxial connector receptacle includes an outer conductor that has a substantially cylindrical-like shape and a central conductor that is disposed at the center of the outer conductor. The outer conductor of the coaxial connector receptacle is to be inserted into the outer conductor 512a of the coaxial connector plug 510. In this case, the central conductor 514a of the coaxial connector plug 510 and the central conductor of the coaxial connector receptacle are connected to each other. In addition, elastic deformation occurs in the outer conductor 512a in such a manner that a cutting portion that has been formed in the outer conductor 512a is slightly widened, and the outer conductor 512a is pressed into contact with the outer peripheral surface of the outer conductor of the coaxial connector receptacle. As a result, the coaxial connector plug 510 and the coaxial connector receptacle are fixed to each other.
There has been a demand for a reduction in the height of the coaxial connector plug 510. Therefore, the height of the outer conductor 512a has been decreasing year-by-year. However, as the height of the outer conductor 512a in the top-bottom direction decreases, the rigidity of the outer conductor 512a decreases. Accordingly, the outer conductor 512a cannot be pressed into contact with the outer peripheral surface of the outer conductor of the coaxial connector receptacle with sufficient strength. As a result, the coaxial connector plug 510 easily separates from the coaxial connector receptacle.